Support Stent for Transvalvular Conduit

ABSTRACT

Miniature axial flow pumps are implanted inside the heart or major arteries to provide hemodynamic support. These pumps commonly utilize tubular blood conduit tubes to transport blood across the aortic valve. The valve leaflets themselves are very thin and flexible, and will seal against the conduit if it is centered within the valve orifice. If the conduit is not centered, a leaflet can be pushed to the side of the aorta, preventing the leaflets from sealing and providing a path for backflow. If the blood flow conduit remains pushed against the side of the valve for a long period of time, thrombus may form in the crevice between the conduit and the aorta, causing serious thromboembolic events such as stroke, if the thrombus breaks free. The present invention provides a conduit support device that retains the conduit centered within the annulus of the natural heart valve. A leaflet valve stent may be combined with a conduit support device comprised of a ring supported by posts attached to the valve stent ring. A blood pump may be attached to the center of a transvalvular support stent, for optimal fixation of the pump with relation to a trileaflet or bi-leaflet tissue or polymer valve.

BACKGROUND OF THE INVENTION

Small less invasive blood pumps are useful to augment the flow ofpatients in late stage heart failure. Early work with these devicesincluded the hemopump U.S. Pat. No. 4,846,152, the Cannula pump U.S.Pat. Nos. 5,376,114, 5,755,784, 5,776,190, 5,888,241, and the HeartWare“longhorn” pump, US patent application No. 20090203957. Temporary axialflow blood pumps implanted for hours or days such as the Impella pump(Statorless intravascular microaxial flow pump U.S. Pat. No. 5,921,913,Intracardiac pump device U.S. Pat. No. 6,139,487 and others) arebecoming widely applied. The Impella is presently FDA approved for useup to six hours. These devices all utilize small diameter tubes(conduits) through which blood transverses cardiac valves, most commonlythe aortic valve. During systole the valve may open, with a portion ofthe flow ejected by the natural heart passing through the orificebetween the leaflets, as well as part of the flow passing through theblood pump conduit. The position of the conduit with these devices islikely to be pushed towards one side of the valve and is not controlledto remain centered within the valve orifice. If the conduit is lodged ina position where it touches against the natural valve annulus, a crevicewill be formed in which thrombus may form. If the conduit then moves,the thrombus could break free becoming a dangerous thromboembolis.

My previously patented valve pump U.S. Pat. No. 7,479,102 is directed tolong term implant where the device can be implanted and remainfunctional for many years. Valve pumps are disclosed in which a verysmall pump is placed in the position of one of the leaflets of theaortic or pulmonic valve, leaving two of the three valve leafletsfunctional. The present invention provides means to hold a conduit orblood pump centered in the valve orifice, so that it will be optimallywashed to prevent thrombus.

OBJECTS OF THE INVENTION

1. It is an object of the invention to provide a device to hold a bloodflow conduit securely in place centered within the orifice of a leafletheart valve.

2. It is a further object of the invention to stabilize a trans-valvularblood flow conduit in a central location within a leaflet typeprosthetic heart valve such that the leaflets can open and close manymillions of cycles without the valve wearing out or developing thrombus.

3. It is another object of the invention to improve the performance ofminiature intravascular cardiac assist systems.

4. An additional object of the invention is to provide an improvedtrans-valvular blood pump fixation device for long term use.

5. A still further object of the invention is to provide a fixationdevice for trans-valvular conduits that will minimize the risk ofthrombus formation by eliminating a crevice formed between the conduitand the side of the valve.

6. Additionally, it is an object of the invention to provide a device tomaintain patency of a trans-valvular conduit within a leaflet valve andthe valve itself, free of thrombus with minimal or no antigoagulationneeded.

7. Another object of the invention is to provide a valved trans-valvularconduit retention device that mates with a miniature trans-valvularblood pump, and retains the pump in the optimal position with relationto a conduit portion of the pump that transverses the valve.

8. It is a further object of the invention to provide a valvedtrans-valvular conduit retention device incorporating tissue valveleaflets that may be wet stored in sterile condition, and at surgery,used with a dry sterilized conduit or blood pump.

THE DRAWINGS

FIG. 1 is a drawing from prior art U.S. Pat. No. 5,376,114 showing ablood pump positioned within the left ventricle and a blood flow conduitpassing through the aortic valve.

FIG. 2 is a drawing from prior art U.S. Pat. No. 7,022,100 showing ablood pump positioned partly within the left ventricle and partly withinthe aorta and having a blood flow conduit that transverses the aorticvalve.

FIG. 3 is a prior art drawing from US patent application No. 20090203957showing a blood pump located within the left ventricle, having a bloodflow conduit passing across the aortic valve, and having a fixationdevice located at the left ventricular apex.

FIG. 4 is a prior art drawing from US patent application No. 20120029265showing a blood pump located within the aorta and having a blood flowconduit passing across the aortic valve, and having a fixation devicelocated within the aorta.

FIG. 5 is a drawing from prior art patent application No. 20120029265showing a fixation device that includes an expandable mesh stent andhinged support arms.

FIG. 6 is a view of an aorta and aortic valve leaflets showing atransvalvular conduit in a non-centered position that pushes one valveleaflet to the side.

FIG. 7 is an illustration of an embodiment of the present inventionincluding a valve stent and conduit support ring in the position withinthe aortic annulus where it is affixed by suturing its sewing cuff tothe aorta.

FIG. 8 is an illustration of a transvalvular conduit located centrallywithin three aortic valve leaflets showing the leaflets closed againstthe conduit.

FIG. 9 is an illustration of an embodiment of the present inventionhaving a support ring maintained in a central position by three posts,and supporting a blood flow conduit within the support ring. The threevalve leaflets are shown in the open position.

FIG. 10 is a longitudinal section of a transvalvular conduit secured toa valve stent mounted central support ring by means of screw threads.

FIG. 11 is an illustration of a transvalvular blood flow conduit held inthe center of the aortic annulus by an embodiment of the presentinvention. An intraventricular blood pump receives blood inflow withinthe left ventricle, and pumps the blood through the center of the aorticvalve via the conduit, and then expels the blood into the aorta.

FIG. 12 is an embodiment of the present invention including a threadedsupport ring adapted to mount a transvalvular blood pump to the supportring.

SPECIFIC DESCRIPTION OF THE INVENTION

Miniature blood pumps have been developed that may be implantedsurgically, such as via an incision in the left ventricular apex, andothers have been developed that may be implanted in the cath lab, via aperipheral vessel such as the femoral artery. A number of these utilizea conduit passed across the aortic valve through which the blood pumpedby the device must pass. Referring to FIG. 1, blood pump 2 has its bloodinflow within the left ventricle 4, and uses a conduit 6 to channelblood across the aortic valve 8, into the aorta 10. FIG. 2 shows a bloodpump 12 located partly in the left ventricle and partly in the aorta,that includes a conduit through which blood flows across the aorticvalve 14 and into the aorta 16.

FIG. 3 shows a blood pump 18, utilizing an outflow conduit 20 to conveyblood across aortic valve 22 into the aorta 24. In FIG. 4, a blood pump26 is located in the aorta 28, and uses an inflow conduit 30 that passesacross the aortic valve 32 and has an inlet opening 34 within the leftventricle. FIG. 5 is an enlarged view of an expandable mesh fixationdevice 36 that holds the blood pump centered in the aorta using posts38, 40 at a position separated from the aortic valve. The function ofthis fixation device is to retain the pump in position so that the pumpand inflow conduit will not shift position due to the reactive force ofthe blood jetting into the aorta.

With small blood pumps that use conduits passing across the aorticvalve, if the conduit is maintained centrally within the valve theleaflets seal against it without regurgitation. If the conduit is smallin diameter, which limits the blood flow to relatively low values, itmay locate between leaflets and seal with little regurgitation. But ifthe conduit is large enough to provide flow above 2-3 L/min, unless itis retained centered in the valve, it can push valve leaflets againstone side of the aorta and prevent the valve from closing effectively.

Referring to FIG. 6, a blood flow conduit 42 compresses one valveleaflet 44 against the aortic wall 46. This prevents the three leafletsfrom sealing against each other, and creates an opening 48 whereregurgitant flow occurs. The present invention provides a supportstructure that holds the conduit centered within the valve leafletswhich seal against the conduit as shown in FIG. 8, thus avoidingregurgitant flow.

Referring to FIG. 7, a support stent 50 is shown within the aorticannulus 52 retained by a sewing cuff 54. In this illustration, forclarity, the three valve leaflet support struts 56, 58, 60 are shownwithout valve leaflets attached. These three struts are joined to oneanother by a integral ring 62. Note that the struts project in thedirection defined from the left ventricular apex towards the aorta. Thestruts actually project into the aorta. Affixed to the ring 62, arethree support posts 64, 66, 68 that attach to a centrally locatedconduit support ring 70. The leaflet support struts, conduit supportring posts, and conduit support ring are all preferably machined out ofa solid bar of polymer, such as homopolymer acetal, or may be molded asone piece. Note that the valve leaflet support struts are located in theaorta 10 , and that the conduit support ring posts and conduit supportring are within the outflow tract of the left ventricle close to theannulus of the aortic valve 52.

Various types of tissue valves are known in the prior art that utilizestents of differing design to support the leaflets. Porcine valveleaflets may be used, pericardial tissue has been used to fashionleaflets, and polymer leaflets have also been developed. The presentinvention provides a leaflet support stent combined with a conduitsupport structure which may be a ring 70, or simply the ends of threeposts 64, 66, 68 without using a ring. If the ends of the posts are usedto hold the conduit centered, the diameter of the conduit must fitclosely within the posts so that it is well retained. The device alsoincludes a sewing cuff 54 that is used to suture the valve and conduitsupport into the aorta using surgical techniques that have been widelyused for aortic valve replacements. Referring to FIG. 11, it is clearlyseen that a blood flow conduit 74 conducts blood flow produced by bloodpump 76 from the left ventricle (arrows), through the center of thevalve support ring 70, and into the aorta at the end of the conduit 78.

As best seen in FIG. 9 with the valve leaflets open, the conduit 74 isheld in the center of the valve between the leaflets 80, 82, 84, by ring70 which is supported by posts 64, 66, 68. The posts, in turn, are heldby the stent support ring 50 that is sutured into the aorta by sewingring 72.

FIG. 10 illustrates an embodiment where the conduit includes a narroweddiameter 86 where it passes through the center of the valve leaflets. Inthis drawing, one leaflet is shown open with flow passing throughindicated by the single arrow 92, and another leaflet is shown in theclosed position with two arrows 94 indicating pressure within the aortathat closes the leaflet 95 against the narrowed portion of the conduit.In actual conditions the three leaflets open and close almostsimultaneously, so the illustration is representative of the twopositions (open and closed) but does not represent the configuration ofthe valve at one point in time. If the conduit includes a narrowedportion where the leaflets are intended to close, some way to retain theconduit in the correct axial position is needed. In the embodiment shownin FIG. 10 the conduit 96 is retained by an internally threaded ring 90attached to the valve stents by post 88. The conduit includes externalthreads 98 that secure it to the threaded ring. This locks the conduitin the correct axial position such that the narrowed lumen 86 isproperly aligned axially with the valve leaflets.

The transvalvular conduit support stent may be configured to directlymount a blood pump by means of a threaded connection 114 or other directattachment mechanisms. Referring to FIG. 12, a blood pump 100 includesan impeller 102 mounted on a rotor having a small diameter elongatedshaft 104 that passes through the center of a narrowed portion of atransvalvular conduit 106 formed integral with the blood pump. Inflowside and outflow side rotor bearings 108,110 support the pump rotorwithin an electric motor (not shown) that powers it via electric cable112. The position of the threads 114 that connect the pump to thesupport ring of the stent is such that the valve leaflets close againstthe narrowed part of the blood pump conduit as seen at 116. Note thatthis illustration, similar to FIG. 10, shows one leaflet open and oneclosed to illustrate both of these positions.

With this embodiment of the invention, the transvalvular support stentis first sutured into the aortic annulus in essentially the same way asan aortic tissue valve implant would be done. Next, the blood pump,which is a separate device, is screwed into the threaded support ring.This is done prior to passing the power cable across the aortic wall (asshown in FIG. 12). After the pump is attached, the power cable is passedacross a hole in the aortic wall and fastened in place. In thisposition, the cable prevents the pump from becoming unscrewed becausethe cable locks it in place rotationally.

The information disclosed in the description of the present invention isintended to be representative of the principles I have described. Itwill thus be seen that the objects of the invention set forth above andthose made apparent from the preceding description are efficientlyobtained and that certain changes may be made in the above articles andconstructions without departing from the scope of the invention. It isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative but notin a limiting sense. It is also understood that the following claims areintended to cover all of the generic and specific features of theinvention herein described and all statements of the scope of theinvention which, as a matter of language, might be said to fall therebetween.

1. (canceled)
 2. (canceled)
 3. A valved conduit support ring adapted tohold a generally tubular member passing therethrough in a centeredposition, said conduit support having two or three cardiac valveleaflets affixed to an annular stent, said conduit support comprised ofa circular or oval ring with two or three valve leaflet support membersaffixed thereto that project axially away from the plane of said supportring in the direction of flow through the valve, and one or more conduitsupport posts also affixed to said ring that project axially in thedirection opposite to the direction of blood flow through said valve. 4.The valved support ring of claim 3 including a threaded support affixedto said posts in an axial position that permits valve leaflets affixedto said leaflet support members to seal against the surface of a taperedtransvalvular conduit in an optimal predetermined axial position bymeans of a threaded member interconnected to said transvalvular conduit.5. The valved support ring of claim 3 in which the trans valvularconduit is a portion of a blood pump that transverses a heart valve. 6.The valved support ring of claim 3 in which the transvalvular conduit isconnected to a blood pump positioned in the aorta or pulmonary artery.7. The valved support ring of claim 3 in which the transvalvular conduitis connected to a blood pump positioned in the left or right ventricle.8. (canceled)